Chlorophyll fluorescence of tropical tree species in a semi-deciduous forest gap
Data
2004-02-01
Autores
Ribeiro, Rafael Vasconcelos
Souza, Gustavo Maia
Manzatto, Angelo Gilberto [UNESP]
Machado, Eduardo Caruso
Oliveira, Ricardo Ferraz de
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade de Investigações Florestais
Resumo
A caracterização dos diferentes grupos ecológicos envolvidos nos processos de formação/sucessão florestal é ainda pouco precisa. Para melhor distinção das classes sucessionais deve-se levar em consideração aspectos ecofisiológicos, como a capacidade de aproveitamento da energia luminosa. O objetivo deste trabalho foi acessar a emissão da fluorescência da clorofila de espécies arbóreas tropicais crescendo em uma clareira de floresta semidecídua. Foram selecionadas três espécies de diferentes grupos ecológicos: Croton floribundus Spreng. (pioneira, P), Astronium graveolens Jacq. (secundária inicial, Si) e Esenbeckia febrifuga A. Juss. (secundária tardia, St). A eficiência quântica potencial (Fv/Fm) e efetiva (deltaF/Fm') do fotossistema II, a taxa aparente de transporte de elétrons (ETR) e os coeficientes de extinção fotoquímica (qP) e não-fotoquímica (qN) da fluorescência da clorofila foram avaliados, utilizando um fluorômetro modulado, entre 7h30 e 11h. Os valores de Fv/Fm permaneceram constantes em St, diminuindo em P e Si a partir das 9h30, indicando a ocorrência de fotoinibição. Entretanto, nas medidas realizadas na presença de luz (deltaF/Fm', ETR, qP e qN), P e Si apresentaram melhor desempenho fotoquímico, ou seja, com o aumento da intensidade luminosa os valores de DF/Fm', ETR e qP foram superiores aos valores de St. Os valores de qN indicaram que P e Si possuem a tendência crescente de dissipar o excesso de energia, sendo observado o contrário em St. A análise de componentes principais (PCA), considerando todos parâmetros avaliados, mostrou clara distinção entre St, P e Si, sendo estas últimas espécies mais próximas. Os resultados dessa análise evidenciam a fluorescência da clorofila como uma ferramenta potencial para diferenciar espécies arbóreas de grupos sucessionais distintos.
The characterization of different ecological groups in a forest formation/succession is unclear. To better define the different successional classes, we have to consider ecophysiological aspects, such as the capacity to use or dissipate the light energy available. The main objective of this work was to assess the chlorophyll fluorescence emission of tropical tree species growing in a gap of a semi-deciduous forest. Three species of different ecological groups were selected: Croton floribundus Spreng. (pioneer, P), Astronium graveolens Jacq. (early secondary, Si), and Esenbeckia febrifuga A. Juss. (late secondary, St). The potential (Fv/Fm) and effective (deltaF/Fm') quantum efficiency of photosystem II, apparent electron transport rate (ETR), non-photochemical (qN) and photochemical (qP) quenching of fluorescence were evaluated, using a modulated fluorometer, between 7:30 and 11:00 h. Values of Fv/Fm remained constant in St, decreasing in P and Si after 9:30 h, indicating the occurrence of photoinhibition. Concerning the measurements taken under light conditions (deltaF/Fm', ETR, qP and qN), P and Si showed better photochemical performance, i.e., values of deltaF/Fm', ETR and qP were higher than St when light intensity was increased. Values of qN indicated that P and Si had an increasing tendency of dissipating the excess of energy absorbed by the leaf, whereas the opposite was found for St. The principal component analysis (PCA), considering all evaluated parameters, showed a clear distinction between St, P and Si, with P and Si being closer. The PCA results suggest that chlorophyll fluorescence may be a potential tool to differentiate tree species from distinct successional groups.
The characterization of different ecological groups in a forest formation/succession is unclear. To better define the different successional classes, we have to consider ecophysiological aspects, such as the capacity to use or dissipate the light energy available. The main objective of this work was to assess the chlorophyll fluorescence emission of tropical tree species growing in a gap of a semi-deciduous forest. Three species of different ecological groups were selected: Croton floribundus Spreng. (pioneer, P), Astronium graveolens Jacq. (early secondary, Si), and Esenbeckia febrifuga A. Juss. (late secondary, St). The potential (Fv/Fm) and effective (deltaF/Fm') quantum efficiency of photosystem II, apparent electron transport rate (ETR), non-photochemical (qN) and photochemical (qP) quenching of fluorescence were evaluated, using a modulated fluorometer, between 7:30 and 11:00 h. Values of Fv/Fm remained constant in St, decreasing in P and Si after 9:30 h, indicating the occurrence of photoinhibition. Concerning the measurements taken under light conditions (deltaF/Fm', ETR, qP and qN), P and Si showed better photochemical performance, i.e., values of deltaF/Fm', ETR and qP were higher than St when light intensity was increased. Values of qN indicated that P and Si had an increasing tendency of dissipating the excess of energy absorbed by the leaf, whereas the opposite was found for St. The principal component analysis (PCA), considering all evaluated parameters, showed a clear distinction between St, P and Si, with P and Si being closer. The PCA results suggest that chlorophyll fluorescence may be a potential tool to differentiate tree species from distinct successional groups.
Descrição
Palavras-chave
Fluorescência da clorofila, ecofisiologia, classes sucessionais, Croton floribundus, Astronium graveolens, Esenbeckia febrifuga, Chlorophyll fluorescence, ecophysiology, successional classes, Croton floribundus, Astronium graveolens, Esenbeckia febrifuga
Como citar
Revista Árvore. Sociedade de Investigações Florestais, v. 28, n. 1, p. 21-27, 2004.